Scenes don’t end. A scene is just a set of instructions sent to the devices that you specified. There isn’t anything in the official smartthings features that tracks what the previous setting was.
So you have two options.
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create a different scene with the devices the way you want them to be and then trigger that when the motion stops. However, that requires knowing in advance what you want those settings to be. You could have different ones for different situations, like one for the evening, one for late at night, etc. but it would still mean deciding in advance what setting you were going to return to.
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use Webcore to keep track of the settings and then revert to them. This could be done, but it is a lot more work and of course you would have to use webcore. (Webcore is essentially a scripting language for smartthings. Very powerful.)
Webcore has its own forum and there are lots of people there who will be glad to help you create the automations you will need. But I don’t know if you’re interested in going that direction.